package com.han.dao;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

//操作数据库的公共类
public class BaseDao {
    private static String driver;
    private static String url;
    private static String username;
    private static String password;

    //静态代码块，类加载时就初始化了
    static {
        Properties properties = new Properties();
        InputStream resourceAsStream = BaseDao.class.getClassLoader().getResourceAsStream("db.properties");
        try {
            properties.load(resourceAsStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
        driver = properties.getProperty("driver");
        url = properties.getProperty("url");
        username = properties.getProperty("username");
        password = properties.getProperty("password");
    }

    //获取数据库的链接
    public static Connection getConnection() throws SQLException, ClassNotFoundException {
        Connection connection = null;
        Class.forName(driver);
        connection = DriverManager.getConnection(url,username,password);
        return connection;
    }

    //编写查询公共类
    public static ResultSet query(Connection connection,PreparedStatement preparedStatement,String sql,Object[] params) throws SQLException {
        preparedStatement = connection.prepareStatement(sql);
        for (int i = 0; i < params.length; i++) {
            preparedStatement.setObject(i+1,params[i]);
        }
        return preparedStatement.executeQuery();
    }

    //编写公共增删改
    public static int update(Connection connection,PreparedStatement preparedStatement,String sql,Object[] params) throws SQLException {
        preparedStatement = connection.prepareStatement(sql);
        for (int i = 0; i < params.length; i++) {
            preparedStatement.setObject(i+1,params[i]);
        }
        int i = preparedStatement.executeUpdate();
        return i;
    }

    //释放资源
    public static boolean closeResource(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet){
        boolean flag = true;
        if (resultSet!=null){
            try {
                resultSet.close();
                resultSet = null;//如果释放失败，就GC回收
            } catch (SQLException throwables) {
                throwables.printStackTrace();
                flag = false;
            }
        }
        if (preparedStatement!=null){
            try {
                preparedStatement.close();
                preparedStatement = null;//如果释放失败，就GC回收
            } catch (SQLException throwables) {
                throwables.printStackTrace();
                flag = false;
            }
        }
        if (connection!=null){
            try {
                connection.close();
                connection = null;//如果释放失败，就GC回收
            } catch (SQLException throwables) {
                throwables.printStackTrace();
                flag = false;
            }
        }
        return flag;
    }
}